The application to vehicles of conversion systems enabling fuelling of the same engine by liquefied petrol or methane gas (CNG) thereby enabling a mixed fuel system has been known of for some time. The systems of the known type are generally composed of a gas tank, a pressure regulator which brings the gas to the right pressure for fuelling the engine, and a series of ducts and relative accessories.
The present coupling device can be used to join pipes and to connect pipes to accessories and valve devices of the system, from the gas-loading device to the gas pressure reducer device.